NOTE: The last few examples of usage are witnessing the fact that the true cause of many diseases were not known to the physicians of ancient times. For example, they did not know about blood cells nor about bacteria causing infection, since the microscope had not yet been invented in the Western World, so they used the term "pneumonia" instead of "pneumonitis" for "inflammation of the lung", naming it "a disease state of the lung".

Look at the Time Table of Medical Innovations (in the Appendix) and note the year (p.115) when the microscope was invented and for what purpose it was first used. Then check how long it took until bacteria were identified as disease causing micro-organisms. See also if you can find out when the cell theory was developed!